Balancing apparatus

ABSTRACT

Balancing apparatus that supports and rotates a body to be measured with a rotating mechanism so that the body vibrates due to the dynamic imbalance thereof. The vibration of the body is transmitted to a vibration member and then detected by a sensor. A vibrator is connected to the vibration member. The vibrator applies to the vibration member a vibration that is an inverse of a vibration that will be generated in the vibration member by an ideal body having an ideal dynamic imbalance. By detecting the vibration remaining in the vibration member, the balancing apparatus measures the deviation of the dynamic imbalance of the body from the ideal dynamic imbalance.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to balancing apparatus thatmeasures dynamic imbalance of a rotating body by detecting vibrationtransmitted to the balancing apparatus from the rotating body.

[0002] Vibration due to imbalance in a rotating body has been a seriousproblem in many industrial fields. In order to prevent such vibration,it is required to dynamically balance the rotating body.

[0003] Some types of rotating body, however, are required to have acertain dynamic imbalance so as to allow a system to which the rotatingbody belongs being dynamically balanced as a whole. For example, a crankshaft, to which pistons or the like are to be coupled, should havedynamic imbalance that cancels the dynamic imbalance generated by thepistons or the like so that serious vibration does not occur in anengine.

[0004] The dynamic imbalance of a rotating body is generally measuredwith balancing apparatus. The rotating body is dynamically balanced byadding or removing mass thereto so as to cancel the measured imbalance.

[0005] If the rotating body is required to have a certain imbalance,mass is added to the rotating body, which mass balances with the desireddynamic imbalance, so that only the deviation of the dynamic imbalancefrom the desired dynamic imbalance will be measured by the balancingapparatus. For example, if the crank shaft is to be measured, a dummyring having the same mass as the piston is mounted to each crank pinduring the measurement.

[0006] The above-mentioned method for measuring dynamic imbalance of acrank shaft, however, requires manually mounting and removing dummyrings whenever a new crank shaft is to be measured, which makesautomation of the measuring process difficult, and also increases thetime required for the measurement.

[0007] Therefore, there is a need for balancing apparatus that iscapable of measuring deviation of the dynamic imbalance of a crank shaftfrom the desired dynamic imbalance thereof without requiring mountingdummy rings to the crank shaft.

[0008] Balancing apparatus measures the dynamic imbalance of a rotatingbody by detecting the vibration transmitted to such balancing apparatusfrom the rotating body with a vibration pick-up. However, thesensitivity of the vibration pick-up, and also the vibrationcharacteristic of the balancing apparatus, may change over time and inaccordance with ambient temperature variation. Accordingly, calibrationof the balancing apparatus should be carried out regularly to ensurecorrect measurement.

[0009] Conventionally, calibration of such balancing apparatus isperformed by providing to the balancing apparatus a standard rotatingbody having no dynamic imbalance, attaching a weight of known mass ontothe standard body, rotating the standard body to measure the dynamicimbalance thereof, and comparing the measurement result with the dynamicimbalance calculated from the mass and position of the weight attachedto the standard body.

[0010] However, it is difficult to automate conventional calibration ofbalancing apparatus, since the calibration process requires manuallyattaching the weight onto the standard body.

[0011] Further, if dynamic imbalance is to be measured for a pluralityof balancing planes of the rotating body, the calibration should becarried out for each balancing plane. That is, the calibration should becarried out several times with the weight being attached to the standardbody in a different balancing plane each time. In this case, the weighthas to be manually attached and removed from the standard body severaltimes which increases the time required for the calibration.

[0012] Therefore, there is a need for balancing apparatus that iscapable of performing calibration without requiring use of a weight.

[0013] In some cases, the vibration characteristic of the balancingapparatus changes significantly, due, for example, to mechanicaldefects. Since correct measurement of dynamic imbalance cannot beachieved in such cases, there is also a need for balancing apparatusthat is capable of automatically detecting such significant changes invibration characteristic.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of the present invention to providebalancing apparatus that is capable of measuring deviation of dynamicimbalance of a rotating body from desired dynamic imbalance thereofwithout requiring manually mounting a weight to the rotating body.

[0015] It is yet another object of the present invention to providebalancing apparatus that is capable of performing calibration thereofwithout requiring manually mounting a weight to a dynamically balancedrotating body utilized for calibration.

[0016] It is yet another object of the present invention to providebalancing apparatus that is capable of automatically detecting abnormalvibration characteristics.

[0017] According to an aspect of the present invention, there isprovided balancing apparatus for rotating a body to be measured with arotating mechanism so that the body vibrates due to the dynamicimbalance thereof. The vibration of the body is transmitted to avibration member and then detected by a sensor. A vibrator is coupled tothe vibration member. In one embodiment of the present invention, thevibrator is for canceling a predetermined vibration of the vibrationmember. For example, the vibrator applies to the vibration member avibration, which is an inverse of an ideal vibration that will begenerated in the vibration member by an ideal body having an idealdynamic imbalance. In this way, the ideal vibration in the vibrationmember can be canceled, and by detecting the vibration remaining in thevibration member, the balancing apparatus can determine the deviation ofthe dynamic imbalance of the body being tested from the ideal dynamicimbalance.

[0018] A memory device may be provided to the balancing apparatus forholding data representing vibration, which will be generated in thevibration member by the ideal body, so that the vibrator can easilyobtain data necessary for vibrating the vibration member as describedabove. It should be noted, the data can be prepared and stored into thememory device by mounting the ideal body to the rotating mechanism,rotating the ideal body to cause vibration to the vibration member, andthen detecting the vibration of the vibration member by the sensor.

[0019] Optionally or additionally, the balancing apparatus may have aprocessor for carrying out calculation for determining dynamic imbalanceof the body from the output of the sensor. The processor also performsmodification of a coefficient utilized in the above-mentionedcalculation. As is well known to those skilled in the art, themodification of such a coefficient can be achieved by generatingvibration in the vibration member with a rotating body having knowndynamic imbalance, and determining the magnitude of the output of thesensor detecting the vibration of the vibration member. In the balancingapparatus of the present invention, however, the modification of thecoefficient is carried out by utilizing a dynamically balanced referencebody, instead of a body having known dynamic imbalance. A referencevibration is further applied to the vibration member by the vibrator.The reference vibration is substantially identical to a vibration thatwill be caused to the vibration member by rotating the reference bodycarrying a predetermined weight at a predetermined location. The datafor generating such reference vibration may be held in a memory deviceof the balancing apparatus.

[0020] In the balancing apparatus arranged as described above, themodification of the coefficient, or calibration of the balancingapparatus, can be performed without actually attaching the weight to thereference body, which allows not only shortening of time required forthe calibration but also automation of the calibration.

[0021] Optionally or additionally, the balancing apparatus may have acontroller for determining whether the balancing apparatus has a defectthat seriously reduces the vibration transmitted from the body to thesensor. The controller determines whether such a defect exists based onvibration detected by the sensor while the vibrator is applying areference vibration to the vibration member, which reference vibrationmay be generated based on data held in a memory device of the balancingapparatus.

[0022] According to another aspect of the present invention, balancingapparatus is provided that includes a rotating mechanism for rotating abody to be measured, a vibration member for being vibrated by the bodybeing rotated by the rotating mechanism, a sensor for detectingvibration of the vibration member, a memory device for holding data ofthe vibration detected by the sensor, a vibrator coupled to thevibration member to apply vibration thereto, and a controller havingfirst and second operation modes. In the first operation mode, thecontroller stores data of the vibration detected by the sensor into thememory device while keeping the vibrator but of operation. In the secondoperation mode, the controller vibrates the vibration member bycontrolling the vibrator based on the data held the memory device.

[0023] In the first operation mode, data on vibration of the vibrationmember caused by, for example, a body having ideal dynamic imbalance ora body having dynamic imbalance suitable for calibrating the balancingapparatus may be sampled and stored into the memory. In the secondoperation mode, the above mentioned data can be utilized for vibratingthe vibration member so that, for example, only the vibration caused bythe deviation of dynamic imbalance of the body from ideal dynamicimbalance thereof remains in the vibration member, or, for generatingvibration in the vibration member that is suitable for carrying outcalibration of the balancing apparatus.

[0024] According to another aspect of the present invention, a methodfor measuring dynamic imbalance of a body is provided. In this method, atest body having unknown dynamic imbalance is rotated to generate afirst vibration in the test body. The first vibration is transmittedfrom the test body to a vibration member. A second vibration is appliedto the vibration member, which second vibration is adjusted tocompletely cancel vibration generated in the vibration member if thetest body has ideal dynamic imbalance. Then, the vibration of thevibration member is detected.

[0025] According to another aspect of the present invention, a methodfor calibrating balancing apparatus is provided, which balancingapparatus applies vibration to a vibration member by rotating a testbody, detects the vibration of the vibration member, and carries out aprocess for determining dynamic imbalance of the test body from thedetected vibration. In this method, a reference body, which has nodynamic imbalance, is arranged such that vibration of the reference bodytransmits to the vibration member. Then, the reference body is rotated.The vibration of the vibration member is detected while applyingreference vibration to the vibration member. The reference vibration issubstantially identical to vibration that will be generated in thevibration member by rotating the reference body carrying a predeterminedweight at a predetermined location. Then, modification of a coefficientutilized in the process for determining the dynamic imbalance is carriedout based on the vibration detected while applying reference vibrationto the vibration member.

[0026] According to another aspect of the present invention, a methodfor testing balancing apparatus is provided, which balancing apparatusgenerates vibration in a vibration member by rotating a test body, anddetermines dynamic imbalance of the test body based on vibration of thevibration member detected by a sensor. In this method, a reference body,which has no dynamic imbalance, is arranged such that vibration of thereference body transmits to the vibration member. The reference body isrotated to cause vibration to the vibration member. The vibration of thevibration member is detected while applying reference vibration to thevibration member. The reference vibration is substantially identical tovibration that will be generated in the vibration member by rotating thereference body carrying a predetermined weight at a predeterminedlocation. Then, it is determined whether the balancing apparatus has adefect that seriously reduces the vibration transmitted from thereference body to the sensor by comparing the vibration detected by thesensor with the reference vibration.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0027]FIGS. 1 and 2 respectively schematically show front and top viewsof the balancing apparatus of a first embodiment of the presentinvention;

[0028]FIGS. 3 and 4 respectively show right and left side views of thebalancing apparatus shown in FIGS. 1 and 2;

[0029]FIG. 5 shows a block diagram of a controller provided to thebalancing apparatus of the first embodiment of the present invention;and

[0030]FIG. 6 shows a front view of the balancing apparatus of a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be described below with reference tothe embodiments shown in the drawings.

[0032]FIGS. 1 and 2 respectively schematically show front and top viewsof the balancing apparatus of a first embodiment of the presentinvention, and FIGS. 3 and 4 respectively show right and left side viewsof the balancing apparatus 100 shown in FIGS. 1 and 2.

[0033] The balancing apparatus 100 is adapted to measure dynamicimbalance of a crank shaft 300, as shown in FIG. 1. The balancingapparatus 100 is provided with a base 102 having first and secondupwardly extending side walls 102 a and 102 b (not shown in FIG. 1, seeFIGS. 2 to 4) and a rigid table 104. The table 104 is supported on thebase 102 between the side walls 102 a and 102 b by means of a pluralityof springs 106 so that the table 104 can vibrate in a substantiallyhorizontal plane. The table 104 is provided with right and left rigidtable walls 110 and 112 mounted on the table 104 near right and leftsides 104 a and 104 b of the table 104, respectively.

[0034] The balancing apparatus 100 has also first and second pairs ofrollers 114 and 116 that are arranged to rotatably support the crankshaft 300 in first and second measuring planes P1 and P2, respectively,which planes are perpendicular to a rotation axis of the crank shaft300. The first pair of rollers 114 are connected to a first pair ofdriven shafts 118 that are held with a pair of bearings 120 provided tothe right table wall 110. Similarly, the second pair of rollers 116 areconnected to a second pair of driven shafts 122 that are held with apair of bearings 124 mounted to the left table wall 112. Thus, the firstand second pairs of rollers 114 and 116 are respectively rotatablysupported by the right and left table walls 110 and 112.

[0035] The first and second pairs of rollers 114 and 116 are rotatablydriven by a driving mechanism that includes a motor 130 provided to thebase 102, and a driving shaft 132 rotatably held below the table 104 bymeans of a plurality of bearings 133 mounted on an under surface 104 cof the table 104.

[0036] The motor 130 has a spindle shaft 130 a that is coupled to thedriving shaft 132 by means of a first pulley 134 fixed to the spindleshaft 130 a, a second pulley 136 fixed to the left end of the drivingshaft 132, and a first endless belt 138 placed around the first andsecond pulleys 134 and 136.

[0037] Referring to FIGS. 1 and 3, the driving shaft 132 is furthercoupled to the first pair of driving shafts 118 by means of third,fourth and fifth pulleys 140, 142 and 144 and a second endless belt 146.The third pulley 140 is fixed to the right end of the driving shaft 132while the fourth and fifth pulleys 142 and 144 are fixed to the firstpair of driven shafts 118 at ends thereof opposite to the first pair ofrollers 114. The second endless belt 146 is placed around the third,fourth and fifth pulleys 140, 142 and 144 to transmit the rotation ofthe driving shaft 132 to the first pair of rollers 114.

[0038] Referring to FIGS. 1 and 4, the driving shaft 132 is also coupledto the second pair of driven shafts 122 by means of a sixth pulley 148fixed to the driving shaft 132 near the second pulley 136, seventh andeighth pulleys 150 and 152 fixed to the second pair of driven shafts 122at ends thereof opposite to the second pair of rollers 116, and a thirdendless belt 154 placed around sixth, seventh and eighth pulleys 148,150 and 152.

[0039] When the balancing apparatus 100 is arranged as described above,the driving force generated by the motor 130 is first transmitted to thedriving shaft 132 via the first endless belt 138. Then, the drivingforce is transmitted to the first and second pairs of driven shafts 118and 122 via the second and third endless belts 146 and 154. As a result,both the first and second pairs of rollers 114 and 116 rotate in thesame direction with the same rotational speed and make the crank shaft300 placed thereon rotate.

[0040] Referring now to FIGS. 1 and 2, the balancing apparatus 100 isfurther provided with right and left vibration pick-ups 155R and 155Lplaced between the first side wall 102 a and the table 104. The rightand left vibration pick-ups 155R and 155L are adapted to detect thevibration of the table 104 in a plane perpendicular to the rotation axisof the crank shaft 300, namely in a plane parallel to the first andsecond measuring planes P1 and P2. Each of the right and left vibrationpick-ups 155R and 155L detects the accelerated velocity of the table 104in two orthogonal directions. In the present embodiment, the twoorthogonal directions are indicated in FIG. 3 by arrows Y and X,respectively. The right and left vibration pick-ups 155R and 155L arelocated so as to detect the vibration of the table 104 near the rightand left table walls 110 and 112, respectively. Typically, the right(left) vibration pick-up 155R (155L) is attached to the side surface ofthe table 104 so that the right (left) vibration pick-up 155R (155L) andthe right (left) table wall 110 (112) are on the same line perpendicularto the rotation axis of the crank shaft 300.

[0041] It should be noted that since the first pair of rollers 114supports the crank shaft 300 in the first measuring plane P1, thevibration of the crank shaft 300 in the first measuring plane P1transmits to the table 104 through the first pair of rollers 114 and theright table wall 110. Thus, the right vibration pick-up 155R attached tothe table 104 near the right table wall 110 detects the vibration of thecrank shaft 300 in the first measuring plane P1. Similarly, the leftvibration pick-up 155L attached to the table 104 near the left tablewall 112 detects the vibration of the crank shaft 300 at the secondmeasuring plane P2, in which the second pair of rollers 116 supports thecrank shaft 300.

[0042] The balancing apparatus 100 is also provided with right and leftpiezoelectric actuators 156R and 156L placed between the second sidewall 102 b and the table 104 in order to vibrate the table 104. Each ofthe right and left piezoelectric actuators 156R and 156L is configuredso as to vibrate in two orthogonal directions in a plane parallel to themeasuring planes P1 and P2. In the present embodiment, the twoorthogonal directions are respectively the X and Y directions, and areindicated by the arrows X and Y in FIG. 3. The right and leftpiezoelectric actuators 156R and 156L are attached to the table 104 nearthe right and left table walls 110 and 112, respectively. Typically, theright (left) piezoelectric actuator 156R (156L) is attached to a sidesurface of the table 104 so that the right (left) piezoelectric actuator156R (156L) and the right (left) table wall 110 (112) are arranged onthe same line perpendicular to the rotation axis of the crank shaft 300.

[0043] The balancing apparatus 100 is further provided with a sensor 158that is located adjacent an end portion of the crank shaft 300, andoutputs a pulse signal whenever a keyway 300 a formed at the end portionof the crank shaft 300 passes by the sensor 158 as the crank shaft 300rotates.

[0044] Further, the balancing apparatus 100 is provided with acontroller 200 (not shown in FIGS. 1 to 4) for controlling the operationof the balancing apparatus 100.

[0045]FIG. 5 shows a block diagram of a controller 200 of the balancingapparatus 100 of the first embodiment of the present invention.

[0046] The controller 200 has a central processing unit (CPU) 202, amemory device 204, an input/output (I/O) port 214, and first, second,third and fourth digital to analog (D/A) converters 206, 208, 210 and212. The controller 200 further has first and second amplifiers 216 and218, first and second analog to digital (A/D) converters 220 and 222,first and second digital filters 224 and 226, and a CPU data bus 228.

[0047] The first and second amplifiers 216 and 218 amplify the analogoutput signals of the right and left vibration pick-ups 155R and 155L,respectively. The first and second A/D converters 220 and 222 covert theanalog output signals of the first and second amplifiers 216 and 218,respectively, into digital signals. The first and second digital filters224 and 226 reduce the noise of the digital signals from the first andsecond A/D converters 220 and 222 and send them to the CPU data bus 228.

[0048] The CPU 202 stores the digital data on the CPU data bus 228 intothe memory device 204. The CPU 202 also generates vibration signalsbased on the data held in the memory device 204 and sends them to theright and left piezoelectric actuators 156R and 156L via the I/O port214 and first, second, third and fourth D/A converters 206, 208, 210 and212 in order to control the actuation of the piezoelectric actuators156R and 156L and thereby control the vibration of the table 104. TheCPU 202 also generates control signals for controlling the actuation ofthe motor 130.

[0049] Hereinafter, the operation of the balancing apparatus 100 will bedescribed. The balancing apparatus 100 has two operation modes, i.e., anideal vibration data sampling mode and a measuring mode. In idealvibration data sampling mode, vibration of an ideal crank shaft havingan ideal dynamic imbalance is measured and data obtained thereby isstored into the memory device 204. In measuring mode, the deviation ofthe dynamic imbalance of a test crank shaft (for which the dynamicimbalance is unknown) from the ideal dynamic imbalance of the idealcrank shaft is measured.

[0050] In ideal vibration data sampling mode, the ideal crank shaft isplaced on the first and second pairs of rollers 114 and 116. Then themotor 130 is actuated to rotate the first and second pairs of rollers114 and 116 and hence the ideal crank shaft. The CPU 202 controls themotor 130 based on the pulse signals generated by the sensor 158 so thatthe ideal crank shaft rotates at a predetermined revolving speed of Nrevolutions per minute (rpm).

[0051] The rotating ideal crank shaft vibrates due to the dynamicimbalance thereof. The vibration of the ideal crank shaft is transmittedthrough the rollers 114 and 116 and the right and left table walls 110and 112 and causes the table 104 to vibrate. The vibration caused to thetable 104 by the ideal crank shaft as described above will be referredto hereinafter as “ideal vibration”.

[0052] Note that the right and left piezoelectric actuators 156R and156L are not actuated during the ideal data sampling mode to ensure thatthe vibration of the table 104 is caused only by the vibration of theideal crank shaft.

[0053] The ideal vibration of the table 104 is detected by the right andleft vibration pick-ups 155R and 155L. The CPU 202 receives datacorresponding to the ideal vibration from the right and left vibrationpick-ups 155R and 155L through the first and second A/D converters 220and 222 for one revolution of the ideal crank shaft, and stores the datainto the memory device 204.

[0054] More specifically, the left vibration pick-up 155L detectsaccelerated velocities in X and Y directions of the table 104 in thevicinity of the left table wall 112 and generates X and Y analog leftvibration signals W_(LX) and W_(LY) corresponding to the detected X andY accelerated velocities. The X and Y analog left vibration signalsW_(LX) and W_(LY) pass through the first amplifier 216 and then enterthe first A/D converter 220 to be converted into X and Y digital leftvibration signals W′_(LX) and W′_(LY). Then, the X and Y digital leftvibration signals W′_(LX) and W′_(LY) are sent to the CPU data bus 228through the first digital filter 224, which reduces the noise of thedigital signals, so that the CPU 202 can capture data corresponding tothe digital vibration signals W′_(LX) and W′_(LY).

[0055] Similarly, the right vibration pick-up 155R detects acceleratedvelocities in X and Y directions of the table 104 in the vicinity of theright table wall 110 and sends X and Y analog right vibration signalsW_(RX) and W_(RY) to the second A/D converter 222 through the secondamplifier 218. The second A/D converter 222 converts the X and Y analogright vibration signals W_(RX) and W_(RY) into X and Y digital rightvibration signals W′_(RX) and W′_(RY) and then sends them to the CPUdata bus 228 through the second digital filter 226, so that the CPU 202can capture data corresponding to the X and Y digital right vibrationsignals W′_(RX) and W′_(RY).

[0056] The CPU 202 monitors the pulse signals generated by the sensor158 and stores, into the memory device 204, data of each of the digitalsignals W′_(LX), W′_(LY), W′_(RX), and W′_(RY) during the period betweentwo consecutive pulse signals. In this manner, the CPU 202 creates foursets of digital data in the memory device 204. The two sets representone cycle of the vibration detected by the right vibration pick-up 155Rin the X and Y directions (which will be referred to hereinafter as Xand Y ideal right vibration data). The other two sets represent onecycle of the vibration detected by the left vibration pick-up 155L inthe X and Y directions (which will be referred to hereinafter as X and Yideal left vibration data).

[0057] In the measuring mode, a test crank shaft having unknown dynamicbalance is placed on the first and second pairs of rollers 114 and 116and rotated by the predetermined revolving speed of N rpm. As a result,the test crank shaft vibrates due to the unknown dynamic balance thereofand, in turn, causes the table 104 to vibrate.

[0058] Then, the CPU 202 generates first and second vibration signalsfor controlling the actuation of the left piezoelectric actuator 156L inthe X and Y directions, respectively, and provides the first and secondvibration signals to the left piezoelectric actuator 156L through thefirst and second D/A converters 206 and 208, respectively. Further, theCPU 202 generates third and fourth vibration signals for controlling theactuation of the right piezoelectric actuator 156R in the X and Ydirections, respectively, and provides the third and fourth vibrationsignals to the right piezoelectric actuator 156R through the third andfourth D/A converters 210 and 212, respectively.

[0059] The first, second, third and fourth control signals arerespectively generated based on the X and Y ideal left vibration dataand the X and Y ideal right vibration data held in the memory device204, and are provided to the right and left piezoelectric actuators 156Land 156R in synchronization with the pulse signals from the sensor 158,so that the resultant vibration of the table 104 is the inverse of theideal vibration. That is, if the ideal vibration can be represented by afunction f=f(θ), where θ indicates the phase of the vibration (or therotation angle of the crank shaft), the first, second, third and fourthcontrol signals actuate the right and left piezoelectric actuators 156Land 156R so that a vibration of the table 104 represented by a functionf=−f(θ) is generated.

[0060] While the right and left piezoelectric actuators 156R and 156Lvibrate the table 104 as described above, the right and left vibrationpick-ups 155R and 155L detect the vibration of the table 104.

[0061] If the test crank shaft has the same dynamic imbalance as theideal crank shaft, the vibration caused by the test crank shaft iscanceled by the inverse vibration generated by the right and leftpiezoelectric actuators 156R and 156L. Thus, the right and leftvibration pick-ups 155R and 155L detect no vibration of the table 104.

[0062] If the dynamic imbalance of the test crank shaft differs fromthat of the ideal crank shaft, the right and left piezoelectricactuators 156R and 156L cannot completely cancel the vibration generatedby the test crank shaft. Thus, the table 104 vibrates due to thedeviation of the dynamic imbalance of the test crank shaft from that ofthe ideal crank shaft.

[0063] The right and left vibration pick-ups 155R and 155L detect thevibration of the table 104 caused by the deviation of the dynamicimbalance from that of the ideal crank shaft, and generate analogsignals in accordance therewith. The generated analog signals are, inturn, amplified by the first and second amplifiers 216 and 218 and thenconverted into digital signals by the first and second A/D converters220 and 222. The CPU 202 stores the digital data coming from the A/Dconverters 202 and 222 into the memory device during the period betweentwo consecutive pulse signals generated by the sensor 158 in accordancewith rotation of the test crank shaft.

[0064] In this way, data is stored in the memory device 204 thatrepresents the deviation of dynamic imbalance of the test crank shaftfrom that of the ideal crank shaft.

[0065]FIG. 6 shows a front view of balancing apparatus 400 of a secondembodiment of the present invention. The balancing apparatus 400 isadapted to measure dynamic imbalance of a rotating body 500. Thebalancing apparatus 400 of the second embodiment has substantially thesame configuration as the balancing apparatus 100 of the firstembodiment of the present invention. However, it operates in differentway. Accordingly, only the operation of the balancing apparatus 400 ofthe second embodiment will be described hereinafter.

[0066] The balancing apparatus 400 of the second embodiment has fouroperation modes, i.e., a reference data sampling mode, a test mode, acalibration mode, and a measuring mode.

[0067] In reference data sampling mode, the table 104 is vibrated by areference body 600 provided with a weight having a known mass W at apredetermined location and data corresponding to the vibration of thetable 104, namely a reference vibration, is sampled. The reference body600 is a dynamically balanced body of the same type as the test body500. Note that, as shown in FIG. 6, the test body 500 (and hence thereference body 600) utilized in the present embodiment has a mainportion 502(602), right and left supporting portion 504 and 506 (604 and606) protruding from the right end 508(608) and left end 510(610) of themain portion 502(602), and a keyway 512(612) formed on thecircumferential surface of an end portion of the body 500 (or thereference body 600).

[0068] In reference data sampling mode, the reference body 600 is placedon the first and second pairs of rollers 114 and 116 so as to besupported at the right and left supporting portions 504 and 506 androtated by a predetermined revolving speed of N rpm. Since the referencebody 600 is dynamically balanced, it does not cause the table 104 tovibrate.

[0069] While the reference body 600 is rotated, zeroing adjustments ofthe right and left vibration pick-ups 155R and 155L are carried out byadjusting the gain of the first and second amplifiers 216 and 218.

[0070] After achieving the zeroing adjustment of the right and leftvibration pick-ups 155R and 155L, the rotation of the reference body 600is temporarily stopped in order to attach the weight. The weight isattached on an outer edge of the left end 510 of the main portion 502 atthe same circumferential location as the keyway 512, for example, asshown in FIG. 6 in broken lines 620.

[0071] Then, the reference body 600 is rotated again at the revolvingspeed of N rpm. This time, the reference body 600 vibrates due to thedynamic imbalance caused by the weight. As a result, the table 104 alsovibrates.

[0072] The left vibration pick-up 155L detects the vibration in X and Ydirections of the table 104 in the vicinity of the left table wall 112and outputs X and Y analog vibration signals W_(LX)(θ) and W_(LY)(θ),where θ represents the phase of the X and Y analog vibration signals, orthe rotating angle of the reference body 600 from the position at whichthe sensor 158 detects the keyway 612.

[0073] The X and Y analog vibration signals W_(LX)(θ) and W_(LY)(θ) passthrough the second amplifier 218 and then enter the second A/D converter222 to be converted into X and Y digital vibration signals W′_(LX)(θ)and W′_(LY)(θ). Then, the X and Y digital vibration signals W′_(LX)(θ)and W′_(LY)(θ) are sent to the CPU data bus 228 through the seconddigital filter 226.

[0074] Similarly, the right vibration pick-up 155R detects the vibrationin X and Y directions of the table 104 in the vicinity of the righttable wall 110 and outputs X and Y analog vibration signals W_(RX)(θ)and W_(RY)(θ) to the first A/D converter 220 through the first amplifier216. The first A/D converter 220 converts the X and Y analog vibrationsignals W_(RX)(θ) and W_(RY)(θ) into X and Y digital vibration signalsW′_(RX)(θ) and W′_(RY)(θ) and then outputs them to the CPU data bus 228through the first digital filter 224.

[0075] The CPU 202 stores, into the memory device 204, data of each ofthe digital vibration signals W′_(LX)(θ), W′_(LY)(θ), W′_(RX)(θ), andW′_(RY)(θ) during the period between two consecutive pulse signalsgenerated by the sensor 158. Thus, four sets of digital data are createdin the memory device 204. Two sets thereof represent one cycle of thevibration of the table 104 in the X and Y directions detected by theleft vibration pick-up 155L, which data sets will be referred tohereinafter as X and Y left weight left vibration data, and the othertwo represent one cycle of the vibration of the table 104 in the X and Ydirections detected by the right vibration pick-up 155R (which data setswill be referred to hereinafter as X and Y left weight right vibrationdata). The four sets of digital data obtained as described above will beutilized in the calibration mode and the test mode.

[0076] Next, the weight is moved to the outer edge of the right end 508of the main portion 502 of the reference body 600 and fixed at the samecircumferential location as the keyway 512. Then, the reference body 600is rotated at N rpm again. The right and left vibration pick-ups 155Rand 155L generate the analog vibration signals W_(LX)(θ), W_(LY)(θ),W_(RX)(θ), and W_(RY)(θ) which are converted into digital vibrationsignals W′_(LX)(θ), W′_(LY)(θ), W′_(RX)(θ), and W′_(RY)(θ) and thenstored into the memory device 204 for one cycle of the vibration. Thus,another four sets of digital data are created in the memory device 204.The sets obtained from the digital vibration signals W′_(LX)(θ) andW′_(LY)(θ) will be referred to hereinafter as X and Y right weight leftvibration data, while the other sets obtained from the digital vibrationsignals W′_(RX)(θ) and W′_(RY)(θ) will be referred to hereinafter as Xand Y right weight right vibration data. The four sets of digital dataobtained as described above will also be utilized in the calibrationmode and the test mode.

[0077] As is well known to those skilled in the art, dynamic imbalanceof the reference body 600 provided with the weight can be represented bytwo vectors U_(L) and U_(R) indicating the magnitudes and angularpositions of the dynamic imbalance in two different balancing planes.

[0078] The vectors U_(L) and U_(R) can be determined from the mass andposition of the weight attached to the reference body 600. Further, asalso well known in the art, the vectors U_(L) and U_(R) can be relatedto vectors f_(L) and f_(R), which represent the magnitudes anddirections of the forces exerted on the first and second rollers 114 and116 by the vibrating reference body 600, using the following equation;$\begin{matrix}{\begin{pmatrix}U_{L} \\U_{R}\end{pmatrix} = {\begin{pmatrix}a_{1} & a_{2} \\a_{3} & a_{4}\end{pmatrix}^{- 1}\begin{pmatrix}f_{L} \\f_{R}\end{pmatrix}}} & (1)\end{matrix}$

[0079] where, a₁, a₂, a₃, and a₄ are constant coefficients.

[0080] If the balancing plane associated with the vector U_(L) isdefined at the left end of the main portion 602 of the reference body600, while the balancing plane associated with the vector U_(R) isdefined at the right end of the main portion 602, and if the weight isattached only to the left end of the main portion 502, the referencebody 600 will only have the dynamic imbalance represented by vectorU_(L). Further, the vectors f_(L) and f_(R) can be determined from the Xand Y left weight left vibration data and the X and Y left weight rightvibration data, respectively. Thus, equation (1) can be rewritten as;$\begin{matrix}{\begin{pmatrix}U_{L1} \\0\end{pmatrix} = {\begin{pmatrix}a_{1} & a_{2} \\a_{3} & a_{4}\end{pmatrix}^{- 1}\begin{pmatrix}f_{L1} \\f_{R1}\end{pmatrix}}} & (2)\end{matrix}$

[0081] where vector U_(L1) indicates the dynamic imbalance determinedfrom the mass and position of the weight attached to the left end of themain portion 602, and f_(L1) and f_(R1) indicate the vectors calculatedbased on the X and Y left weight left vibration data and the X and Yleft weight right vibration data, respectively. From equation (2), theconstant coefficients a₁ and a₃ are obtained as; $\begin{matrix}{a_{1} = \frac{U_{L1}}{f_{L1}}} & (3) \\{a_{3} = \frac{U_{L1}}{f_{R2}}} & (4)\end{matrix}$

[0082] On the contrary, if the weight is attached only at the right endof the main portion 602, the dynamic imbalance of the reference body 600can be represented only by the vector U_(R), and the vectors f_(L) andf_(R) can be determined from the X and Y right weight left vibrationdata and the X and Y right weight right vibration data, respectively.Thus, equation (1) can be rewritten as; $\begin{matrix}{\begin{pmatrix}0 \\U_{R2}\end{pmatrix} = {\begin{pmatrix}a_{1} & a_{2} \\a_{3} & a_{4}\end{pmatrix}^{- 1}\begin{pmatrix}f_{L2} \\f_{R2}\end{pmatrix}}} & (5)\end{matrix}$

[0083] where vector U_(R2) indicate the dynamic imbalance calculatedfrom the mass and position of the weight attached at the right end ofthe main portion 602, and f_(L2) and f_(R2) indicate the vectorscalculated based on the X and Y right weight left vibration data and theX and Y right weight right vibration data, respectively. From equation(5), the constant coefficients a₂ and a₄ are obtained as;$\begin{matrix}{a_{2} = \frac{U_{R2}}{f_{L2}}} & (6) \\{a_{4} = \frac{U_{R2}}{f_{R2}}} & (7)\end{matrix}$

[0084] In the vibration data sampling mode, the CPU 202 calculates theconstant coefficients a₁, a₂, a₃ and a₄ based on the equations (3), (4),(6) and (7) and stores the calculated values into the memory device 204for later use. Then, the vibration data sampling mode terminates.

[0085] The operation of the balancing apparatus 400 in the test modewill now be described. The test mode is carried out in order to checkfor defects of the balancing apparatus 400 that may seriously reducetransmission of the vibration of the rotating body to the vibrationpick-ups 155R and 155L.

[0086] In the test mode, the reference body 600 is placed on the firstand second pairs of rollers 114 and 116 and rotated at a revolving speedof N rpm. Then, the CPU 202 transfers the X and Y left weight leftvibration data to the left piezoelectric actuator 156L through the firstand second D/A converters 206 and 208, respectively, in synchronizationwith the pulse signals from the sensor 158. The CPU 202 also transfersthe X and Y left weight right vibration data to the right piezoelectricactuator 156R through the third and fourth D/A converters 210 and 212,respectively, in synchronization with the pulse signals from the sensor158. As a result, the right and left piezoelectric actuators 156R and156L cause the table 104 to vibrate, and hence to cause the referencebody 600 to vibrate. The vibration caused being substantially identicalto the vibration caused by the reference body 600 provided with theweight at the left end of the main portion 602.

[0087] In the meantime, the right and left vibration pick-ups 155R and155L detect the vibration of the table 104. The CPU 202 calculates thedeviation of the output signals of the right and left vibration pick-ups155R and 155L from the X and Y left weight right and left vibration databased on the following equations; $\begin{matrix}{\delta_{1} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{LX}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{LLX}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (8) \\{\delta_{2} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{LY}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{LLY}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (9) \\{\delta_{3} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{RX}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{LRX}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (10) \\{\delta_{4} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{RY}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{LRY}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (11)\end{matrix}$

[0088] where M_(LLX)(2πm/M) and M_(LLY)(2πm/M) represent X and Y leftweight left vibration data, respectively, and M_(LRX)(2πm/M) andM_(LRL)(2πm/M) represent the X and Y left weight right vibration data,respectively. M indicates the number of data samples per revolution ofthe reference body 600.

[0089] The deviations δ₁, δ₂, δ₃ and δ₄ are compared with respectivethreshold values Th₁, Th₂, Th₃ and Th₄, which are determined empiricallyand vary with the form and size of the reference body 600. When one ofthe deviations δ₁, δ₂, δ₃ and δ₄ exceeds the corresponding thresholdvalue, it is judged that the balancing apparatus 400 has a defect thatseriously reduces the vibration transmitted from the reference body 600to the right and left vibration pick-ups 155R and 155L. In this case,the CPU 202 provides a warning to the operator through, for example, adisplay unit (not shown), and then terminates the test mode operation.

[0090] on the contrary, if all of the deviations δ₁, δ₂, δ₃ and δ₄ arewithin the corresponding threshold values, the same process is repeatedby sending the X and Y right weight left vibration data and the X and Yright weight right vibration data, which are held in the memory device204, to the right and left piezoelectric actuators 156R and 156L. Thistime, the deviation of the output signals of the right and leftvibration pick-ups 155R and 155L are obtained using the followingequations; $\begin{matrix}{\delta_{1} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{LX}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{RLX}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (12) \\{\delta_{2} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{LY}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{RLY}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (13) \\{\delta_{3} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{RX}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{RRX}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (14) \\{\delta_{4} = {\frac{1}{M}{\sum\limits_{m = 1}^{M}\quad \left( {{W_{RY}\left( {2\quad \pi \quad {m/M}} \right)} - {M_{RRY}\left( {2\quad \pi \quad {m/M}} \right)}} \right)^{2}}}} & (15)\end{matrix}$

[0091] where M_(RLX)(2πm/M), M_(RLY)(2πm/M), M_(RRX)(2πm/M) andM_(RRL)(2πm/M) represent X and Y right weight left vibration data and Xand Y right weight right vibration data, respectively.

[0092] Again, if one of the deviations δ₁, δ₂, δ₃ and δ₄ exceeds thecorresponding threshold value, the CPU 202 provides a warning to theoperator and then terminates the test mode operation. On the contrary,if all of the deviations δ₁, δ₂, δ₃ and δ₄ are within the correspondingthreshold values, it is judged that the balancing apparatus 400 has nodefect and the CPU 202 provides this result to the operator through, forexample, the display unit. Then, the test mode operation terminates.

[0093] The calibration mode of the balancing apparatus 400 of the secondembodiment of the present invention will now be described. Thecalibration mode modifies the constant coefficients a₁, a₂, a₃ and a₄,in order to prevent measurement error caused by changes in sensitivityof the right and left vibration pick-ups 155R and 155L that may becaused, for example, by variation of ambient temperature. Note that, thecalibration mode is preferably carried out only when the test mode hasnot found a defect of the balancing apparatus 400.

[0094] In calibration mode, the reference body 600 is placed on thefirst and second pairs of rollers 114 and 116 and rotated at a revolvingspeed of N rpm. Then, the table 104, and hence the reference body 600,is vibrated by providing the X and Y left weight left vibration data andalso the X and Y left weight right vibration data to the right and leftpiezoelectric actuators 156R and 156L via the first, second, third andfourth D/A converters 206, 208, 210 and 212. As a result, the table 104is caused to vibrate. The vibration caused is substantially identical tothe vibration caused by the reference body 600 having the weight at theleft end of the main portion 602 thereof although no weight is attachedthereto.

[0095] Next, the CPU 202 calculates the vectors f_(L1) and f_(R1) fromthe output signals currently generated by the right and left vibrationpick-ups 155R, 155L (W_(LX)(θ), W_(LY)(θ), W_(RX)(θ) and W_(RY)(θ)).Then, the constant coefficients a₁ and a₃ are determined by substitutingthe obtained vectors f_(L1) and f_(R1) into equations (3) and (4). Next,the old values of the constant coefficients a₁ and a₃ held in the memorydevice 204 are replaced with the new values. In this way, themodification of the constant coefficients a₁ and a₃ is carried out.

[0096] Next, the CPU 202 sends the X and Y right weight left vibrationdata and also the X and Y right weight right vibration data to the rightand left piezoelectric actuators 156R, 156L. In this way, the table 104is caused to vibrate. The vibration caused is substantially identical tothe vibration generated by the reference body 600 having the weight atthe right end of the main portion 602 thereof.

[0097] Next, the CPU 202 calculates the vectors f_(L2) and f_(R2) fromthe output signals currently generated by the right and left vibrationpick-ups 155R and 155L (W_(LX)(θ), W_(LY)(θ), W_(RX)(θ) and W_(RY)(θ)).Then, the constant coefficients a₂ and a₄ are determined by substitutingthe obtained vectors f_(L2) and f_(R2) into equations (6) and (7). Then,the old values of the constant coefficients a₂ and a₄ in the memorydevice 204 are replaced with the new values.

[0098] After saving the constant coefficients a₂ and a₄, the operationof the calibration mode terminates.

[0099] The measuring mode of the balancing apparatus 400 of the secondembodiment of the present invention will now be described.

[0100] In this mode, the test body 500 having unknown dynamic balance isplaced on the first and second pairs of rollers 114 and 116 and rotatedat a revolving speed of N rpm. The test body rotating at N rpm vibratesdue to the dynamic imbalance thereof. The right and left vibrationpick-ups 155R and 155L detect the vibration of the test body via thetable 104 and generate output signals W_(LX)(θ), W_(LY)(θ), W_(RX)(θ)and W_(RY)(θ). The CPU 202 receives the output signals of the right andleft vibration pick-ups 155R and 155L and determines therefrom thevectors f_(L) and f_(R) of the forces exerted on the first and secondrollers 114 and 116 from the test body 600. Then, the vectors f_(L) andf_(R), and also the constant coefficients a₁, a₂, a₃ and a₄ held in thememory device 204 are substituted into equation (1). As a result, thevectors U_(L) and U_(R) indicating the dynamic imbalance of the testbody can be obtained.

[0101] While the present invention has been described with particularreference to its preferred embodiments, it will be understood by thoseskilled in the art that changes may be made and equivalents may besubstituted for elements of the preferred embodiments without departingfrom the present invention. In addition, modifications may be made toadapt a particular situation and material to a teaching of the presentinvention without departing from the essential teachings of the presentinvention. For example, in the first embodiment of the presentinvention, the ideal dynamic imbalance of the ideal crank shaft can bedivided into a plurality of pieces of ideal dynamic imbalance eachdefined on a balancing plane defined at a different crank pin of thecrank shaft. Each piece of ideal dynamic imbalance generates in thevibration member a particular vibration as the crank shaft rotates,which can be canceled with the inverse vibration thereof.

[0102] In the first embodiment of the present invention, the data ofeach inverse vibration may be stored into the memory device of thebalancing apparatus, and the piezoelectric actuators may be operated togenerate in the vibration member a composite vibration of the inversevibrations held in the memory device.

[0103] A plurality of crank pin sensors may be further provided to thebalancing apparatus of the first embodiment of the present invention,which crank pin sensors detect an angular position of respective ones ofthe crank pins of the rotating crank shaft. The composite vibration ofthe inverse vibrations may be generated taking into account the angularpositions of the crank pins detected by the crank pin sensors so as todecrease errors in dynamic imbalance measurement due to the effect ofangular positional error of the crank pins of the crank shaft to bemeasured.

[0104] The present disclosure relates to the subject matters containedin Japanese Patent Applications No. P2002-141486, filed on May 16, 2002,and No. P2002-164232, filed on Jun. 5, 2002, which are expresslyincorporated herein by reference in their entireties.

What is claimed is:
 1. Balancing apparatus, comprising: a rotatingmechanism for rotating a body to be measured; a vibration member forbeing vibrated by the body being rotated by said rotating mechanism; asensor for detecting vibration of said vibration member; and a vibratorcoupled to said vibration member for vibrating said vibration member,wherein, in use, said sensor detects composite vibration generated insaid vibration member by said body and said vibrator.
 2. The balancingapparatus according to claim 1, wherein said vibrator vibrates saidvibration member so as to cancel a predetermined vibration of saidvibration member.
 3. The balancing apparatus according to claim 1,wherein said vibrator applies to said vibration member a vibration,which is an inverse of a vibration that will be caused to said vibrationmember by an ideal body having an ideal dynamic imbalance.
 4. Thebalancing apparatus according to claim 3, further comprising a memorydevice for holding data representing vibration which will be generatedin said vibration member by the ideal body, wherein said vibratorvibrates said vibration member based on the data held in said memorydevice.
 5. The balancing apparatus according to claim 4, wherein saiddata in said memory device is prepared from vibration detected by saidsensor when said vibration member is vibrated by the ideal body mountedto and rotated by said rotating mechanism.
 6. The balancing apparatusaccording to claim 1, further comprising a processor for carrying outcalculation for determining dynamic imbalance of the body from output ofsaid sensor, and wherein said processor performs modification of acoefficient utilized in said calculation, said modification beingcarried out based on output of said sensor while said rotating mechanismis rotating a dynamically balanced reference body as well as saidvibrator is applying to said vibration member a reference vibration,said reference vibration being substantially identical to vibration thatwill be caused to said vibration member by rotating the reference bodyprovided with a weight at a predetermined location.
 7. The balancingapparatus according to claim 6, further comprising a memory device forholding data for generating said reference vibration.
 8. The balancingapparatus according to claim 1, further comprising a controller fordetermining whether said balancing apparatus has a defect that seriouslyreduces the vibration transmitted from the body to said sensor, based onvibration detected by said sensor while said vibrator is applying areference vibration to said vibration member.
 9. The balancing apparatusaccording to claim 8, further comprising a memory device for holdingdata for generating said reference vibration.
 10. A balancing apparatus,comprising: a rotating mechanism for rotating a body to be measured; avibration member for being vibrated by the body being rotated by saidrotating mechanism; a sensor for detecting vibration of said vibrationmember; a memory device for holding data of the vibration detected bysaid sensor; a vibrator coupled to said vibration member for applyingvibration thereto; and a controller having first and second operationmodes, said controller in said first operation mode storing data of thevibration detected by said sensor into said memory device while keepingsaid vibrator out of operation, said controller in said second operationmode vibrating said vibration member by controlling said vibrator basedon said data held said memory device.
 11. A method for measuring dynamicimbalance of a body, comprising: rotating a test body having unknowndynamic imbalance to generate a first vibration in the test body; saidfirst vibration being transmitted from the test body to a vibrationmember; applying a second vibration to the vibration member, the secondvibration being adjusted to cancel vibration generated in the vibrationmember if the test body has ideal dynamic imbalance; detecting anyvibration of the vibration member.
 12. The method according to claim 11,further comprising preparing data for generating the second vibration ina memory device in advance of applying the second vibration to thevibration member.
 13. The method according to claim 12, whereinpreparing data for generating the second vibration includes: rotating astandard body having the ideal dynamic imbalance; transmitting vibrationgenerated in the standard body to the vibration member; detecting thevibration of the vibration member; and storing data of the detectedvibration into the memory device.
 14. A method for calibrating balancingapparatus, the balancing apparatus applying vibration to a vibrationmember by rotating a test body, detecting the vibration of the vibrationmember, and carrying out a process for determining dynamic imbalance ofthe test body from the detected vibration, said method comprising:arranging a reference body such that vibration of the reference bodytransmits to the vibration member, said reference body having no dynamicimbalance; rotating the reference body; detecting vibration of thevibration member while applying reference vibration to the vibrationmember, the reference vibration being substantially identical tovibration generated in the vibration member by rotating the referencebody provided with a weight at a predetermined location; and modifying acoefficient utilized in the process for determining the dynamicimbalance based on the vibration detected while applying referencevibration to the vibration member.
 15. The method according to claim 14,further comprising: rotating the reference body provided with the weightat the predetermined location to vibrate the vibration member; detectingthe vibration of the vibration member; storing data of the detectedvibration into a memory device; and generating the reference vibrationfrom the data held in the memory device.
 16. A method for testingbalancing apparatus that determines dynamic balance of a test body bygenerating vibration in a vibration member by rotating the test body,and detecting the vibration of the vibration member by a sensor, themethod comprising: arranging a reference body such that vibration of thereference body transmits to the vibration member, said reference bodyhaving no dynamic imbalance; rotating the reference body; detectingvibration of the vibration member while applying reference vibration tothe vibration member, the reference vibration being substantiallyidentical to vibration generated in the vibration member by rotating thereference body provided with a weight at a predetermined location; anddetermining whether the balancing apparatus has a defect that seriouslyreduces the vibration transmitted from the reference body to the sensorby comparing the vibration detected by the sensor with the referencevibration.
 17. The method according to claim 16, wherein determiningwhether the balancing apparatus has the defect includes: calculatingdeviation of the vibration detected by the sensor from the referencevibration; and comparing the deviation with a predetermined threshold.18. The method according to claim 16 or 17, further comprising providinga warning to an operator of the balancing apparatus when it isdetermined that the balancing apparatus has the defect.
 19. The methodaccording to claim 16, further comprising: rotating the reference bodyprovided with the weight at the predetermined location to vibrate thevibration member; detecting the vibration of the vibration member;storing data of the detected vibration into a memory device; andgenerating the reference vibration from the data held in the memorydevice.
 20. The method according to claim 16, further comprising:carrying out modification a coefficient utilized in a processing fordetermining the dynamic imbalance of the test body from output of thesensor, said modification being carried out when it is determined thebalancing apparatus does not have the defect.